A filter cigarette-manufacturing machine includes a feeding path for feeding cigarette rods sideways. In other words, cigarette rods are fed in the perpendicular direction relative to their axis. In the cigarette rod-feeding process, a cigarette rod is first cut into equal parts to form two cigarettes. Thereafter, a space is secured between the two cigarettes to dispose a filter plug therein, and then the cigarettes are then in closely contact with both ends of the filter plug to form a cigarette/plug assembly.
Subsequently, the cigarette/plug assembly is wound with a tip paper piece to be formed into a double filter cigarette. The double filter cigarette is then cut into equal parts, thereby obtaining discrete filter cigarettes.
A filter cigarette having an outer surface with any defect in appearance, such as dirt, stain and the like, is a defective product. The defective product must be ejected from the feeding path.
To eject defective products from the feeding path, it is required to detect defects in appearance of products as rod-like articles, namely cigarettes or filter cigarettes, in the feeding process thereof. Generally, the detection is performed by using an inspection camera for imaging the outer peripheral surface of a rod-like article.
With respect to the rod-like article on the feeding path, however, what the inspection camera can image is only a part of the outer peripheral surface of the rod-like article, the part facing the inspection camera. Therefore, imaging the whole area of the outer peripheral surface of the rod-like article requires a plurality of inspection cameras.
More specifically, the feeding path is generally defined by a drum train including a plurality of fluted drums ranged in the feeding path. Rod-like articles on the drum train are conveyed while being sequentially transferred from a fluted drum to the adjacent fluted drum. Accordingly, every time the rod-like article is transferred to the next fluted drum, a different part of the outer peripheral surface of the rod-like article is brought to face outward in a radial direction of the fluted drum. If a plurality of inspection cameras are located in proper positions on the feeding path, these inspection cameras can image different parts of the outer peripheral surface of the rod-like article one after another. As a result, the image of the entire outer peripheral surface of the rod-like article can be obtained by collecting image data from each inspection camera.
It is not easy, however, to secure locating spaces for a plurality of inspection cameras in the feeding path. Moreover, the use of a plurality of inspection cameras raises the cost of an appearance inspection device.
On the other hand, in the feeding process of rod-like articles, if a rod-like article is rotated around its axis when passing the visual field of an inspection camera, it is possible for one inspection camera to image the entire outer peripheral surface of the rod-like article. However, the speed of feeding cigarettes or filter cigarettes on the feeding path is extremely high, so that it is impossible to rotate the rod-article at 360° in a short interval where the rod-like article passes the visual field of the inspection camera.